In order to efficiently utilize a bus system, when a new job occurs, the preferences assigned to jobs is determined in accordance with the volumes of the data remaining for unprocessed jobs, and the job that has been determined to have the highest preference is permitted to use the bus. In addition, when a new job occurs, for unprocessed jobs, job preferences are determined in accordance with a necessary channel count x necessary cycle count value, and a job that is determined to have the highest preference is permitted to use the bus. Furthermore, the nodes are managed so as to specify the order in which the bus can be obtained, and the node that used the bus the latest is permitted to use the bus.